JPH0692774A - Method for growing silicon single crystal - Google Patents

Abstract

PURPOSE:To obtain the uniform Si single crystal which contains oxygen of an arbitrary concn. from 2X10<17> up to 2X10<18>pieces/cm<3> in the crystal without having growth striae. CONSTITUTION:The magnetic field which is parallel with the crystal growth direction and axisymmetrical therewith is impressed by a magnet 1 to the Si melt 10 in a crucible 9, and further, the convection of the melt in the crucible is observed by an X-ray fluoroscopic method and the intensity of the magnetic field is so controlled that the flow velocity attains <=7.0mm/sec at all times, by which the growth striae in the crystal are eliminated and the oxygen concn. in the crystal is controlled in growing the Si single crystal by a CZochralski method under magnetic field impression.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing a silicon (Si) single crystal by the magnetic field applied Czochralski method.

[0002]

2. Description of the Related Art In the conventional method of growing a Si single crystal by the magnetic field applied Czochralski method, in order to obtain a uniform single crystal without growth fringes, a magnetic field of 1000 to 3000 gauss (G) is applied to the inside of the crucible. Crystals were grown by stopping the convection of the melt. However, the oxygen concentration in the crystal was 2 × 10 ¹⁷ because the supply of oxygen from the crucible where convection stopped stopped.
It was below the number of pieces / cm ³ .

[0003]

As described above, in the conventional method for growing a Si single crystal by the magnetic field application Czochralski method, a magnetic field is applied to stop convection and grow the crystal, so that the oxygen concentration in the crystal is increased. Was 2 × 10 ¹⁷ pieces / cm ³ or less. For this reason, it was not possible to obtain a uniform Si single crystal having no growth fringes containing oxygen of 5 × 10 ¹⁷ atoms / cm ³ or more, which is necessary for the strength of the wafer and gettering of impurities.

An object of the present invention is to provide a single crystal growth method for obtaining a uniform Si single crystal free of growth fringes, containing arbitrary oxygen of 2 × 10 ¹⁷ to 2 × 10 ⁸ pieces / cm ^{3 in the} crystal.

[0005]

A method for growing a silicon single crystal according to the present invention is a Si by a magnetic field applied Czochralski method.
In the single crystal growth method, a magnetic field parallel to the single crystal growth direction and axisymmetric is applied, and the convection of the silicon melt in the crucible is observed by X-ray fluoroscopy, and the flow velocity is always 7.0 m.
The oxygen concentration is controlled by adjusting the strength of the magnetic field so as to be m / sec or less.

[0006]

In the present invention, by applying a magnetic field parallel to the crystal growth direction and axisymmetrically, convection in the melt is made axisymmetric, and the flow velocity is measured by X-ray fluoroscopy, and the flow velocity of convection is 0 to 7 By setting the range of 0.0 mm / sec, a homogeneous Si single crystal free from growth fringes can be obtained with an oxygen concentration in an arbitrary range. By this method, oxygen is changed from 2x10 ¹⁷ to 2x10 ¹⁸
It is possible to obtain a homogeneous Si single crystal having no growth fringes, which is included in any range up to the number of pieces / cm ³ .

According to the present invention, by applying a magnetic field parallel to the crystal growth direction and axisymmetric with a strength of 400 G at the center position of the melt in the crucible, the convection in the melt becomes an axisymmetric flow. It has been confirmed by X-ray fluoroscopy that the flow velocity is 7.0 mm / sec or less. In the case of such an axisymmetric flow having a low flow velocity, it is considered that there is no temperature fluctuation at the solid-liquid interface and no growth fringes occur. Further, if the convection flow is slow but the convection is not completely stopped, this convection can transport oxygen dissolved from the quartz crucible into the crystal. Therefore, S with an oxygen concentration of 5 × 10 ¹⁷ pieces / cm ³ or more
An i single crystal can also be obtained. Therefore, there is no growth stripe and the oxygen concentration is 2 × 10 ¹⁷ to 2 × 10 ¹⁸ pieces / cm 3.
Si single crystals up to ³ can be obtained.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a crystal growth apparatus used in one embodiment of the present invention. In FIG. 1, the crystal growth apparatus includes a single crystal growth furnace 3, an X-ray generator 4, an X-ray camera 5, a TV monitor 6, an image processing unit, which is provided with a donut-shaped magnet 1, a magnet controller 2, a crucible 9, and the like. The device 7 and the computer 8 are mainly included. The operation for growing a single crystal will be described below.

First, polycrystalline silicon is put into a quartz crucible 9 in the crystal growth furnace 3 and heated and melted to form a melt 10.
Next, a tungsten tracer for measuring the flow velocity is melted 1
Add to 0. Next, X-rays are generated from the X-ray generator 4, the inside of the crystal growth furnace 3 and the inside of the quartz crucible 9 are seen through by an X-ray camera, and the see-through image is processed through the image processing device 7 and the computer 8. , Trace the movement of the tracer and measure the flow rate of the melt. The movement of the tracer at this time can be observed on the television monitor 6.

Next, a magnetic field is applied by the magnet controller 2 and the magnet 1 to change the convection flow velocity of the melt so as to obtain a desired oxygen concentration, and the growth of a single crystal is started. When the flow velocity changes during the growth, the magnetic field intensity is changed by the magnet controller 2 so that the flow velocity is always constant.

After the growth of the single crystal is completed, the crystal growth furnace 3 is cooled and the Si single crystal 11 is taken out.

When a Si single crystal 11 having a diameter of 2 inches is grown from a crucible 9 having a diameter of 3 inches in the single crystal growing furnace 3, the strength of the magnetic field is changed from 0 to 1000 G at the central position of the melt 10. It was FIG. 2 shows the result of measuring the convection flow velocity of the Si melt at this time.

From FIG. 2, when a magnetic field of 400 G is applied, the flow rate of the silicon melt becomes 6.5 mm / sec and 7.0.
It can be seen that a flow velocity of mm / sec or less can be obtained.

As Examples 1 to 5, crystals were grown by applying magnetic fields of various strengths so that the flow rate of the Si melt was 7.0 mm / sec or less. Table 1 shows the result of measuring the oxygen concentration in the crystal grown under these conditions by FT-IR and examining the presence or absence of growth stripes by X-ray topography. In addition, as a comparative example, when the magnetic field is not applied and when the magnetic field is applied, the flow velocity becomes 7.0 mm / sec or more 100 G
Also, the case of growing a crystal by applying a magnetic field of 200 G was also described.

[0015]

[Table 1]

From Table 1, a magnetic field parallel and axisymmetric to the crystal growth direction is applied, and the flow velocity of the Si melt convection is 7.0 mm /
By setting it to sec or less, there are no growth stripes and 2 × 10
It was confirmed that Si single crystals containing oxygen from ¹⁷ to 2 × 10 ¹⁸ pieces / cm ³ were obtained.

[0017]

As described above, according to the present invention, 2 × 10
An Si single crystal containing oxygen in an arbitrary range of ¹⁷ to 2 × 10 ¹⁸ pieces / cm ³ and having no growth fringes can be grown by the magnetic field applied Czochralski method.

[Brief description of drawings]

FIG. 1 is a block diagram of a crystal growth apparatus used in an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between magnetic field strength and the flow rate of Si melt.

[Explanation of symbols]

 1 crystal growth furnace main body 2 magnet 3 magnet controller 4 X-ray generator 5 X-ray camera 6 TV monitor 7 image processor 8 computer 9 crucible 10 melt 11 Si single crystal

Claims (1)

[Claims] 1. In a method for growing a silicon single crystal by a magnetic field application Czochralski method, a magnetic field is applied in parallel and axisymmetrically to the growth direction of the silicon single crystal to adjust the strength of the magnetic field to form growth stripes in the crystal. A method for growing a silicon single crystal, characterized in that the convection velocity of the silicon melt in the crucible is set to 0 to 7.0 mm / sec in order to eliminate and control the oxygen concentration in the crystal.